1. Field of the Invention
The present invention relates to a driving apparatus for driving an optical component or the like using a motor.
2. Description of the Related Art
As a first conventional example, a motor that has a reduced dimension in a direction of a rotating shaft and provides an improved output has been suggested in, for example, Japanese Patent Laid-Open No. 2004-242453.
FIG. 10 is an exploded perspective view illustrating the motor of the first conventional example, and FIG. 11 is a longitudinal sectional view of the motor shown in FIG. 10.
Referring to FIGS. 10 and 11, the motor of the first conventional example includes a cylindrical magnet 106 divided into N portions along the circumferential direction, the N portions being alternately polarized to different poles; a rotor shaft 107 fixed to the inner periphery of the magnet 106 and made of soft magnetic material; a first coil 102 disposed adjacent to the magnet 106 in an axial direction from the rotor shaft 107; a first outer magnetic-pole portion 101a that is excited by the first coil 102, that extends through the inner periphery of the first coil 102, and that is disposed so as to face an outer peripheral surface of the magnet 106 in a predetermined angular range in such a manner that a gap is provided between the first outer magnetic-pole portion 101a and the outer peripheral surface of the magnet 106; and a second coil 104 disposed adjacent to the magnet 106 in the axial direction of the rotor shaft 107 on substantially the same plane as the first coil 102; and a second outer magnetic-pole portion 101b that is excited by the second coil 104, that extends through the inner periphery of the second coil 104, and that is disposed so as to face the outer peripheral surface of the magnet 106 in a predetermined angular range in such a manner that a gap is provided between the second outer magnetic-pole portion 101b and the outer peripheral surface of the magnet 106. The phase of the second outer magnetic pole unit 101b with respect to the polarized portions of the magnet 106 is shifted by (180/N) degrees from that of the first outer magnetic pole unit 101a. The first outer magnetic-pole portion 101a, the second outer magnetic-pole portion 101b, and a flat-plate portion 101c that connects the first outer magnetic pole unit 101a and the second outer magnetic pole unit 101b at one end thereof form an integrated stator 101. The rotor shaft 107 is rotatably retained by a bearing 110 attached to the stator 101 and a bearing 109 attached to a cover 108.
In this motor, the rotor shaft 107 is rotated by switching the energizing directions of the first coil 102 and the second coil 104 and changing the polarities of the first outer magnetic pole unit 101a and the second outer magnetic pole unit 101b. 
In this motor, magnetic flux that is generated when the coils are energized flows from the outer magnetic-pole portions to the rotor shaft (inner magnetic-pole portions) through the magnet or from the rotor shaft (inner magnetic-pole portions) to the outer magnetic-pole portions through the magnet, and efficiently affects the magnet placed between the inner and outer magnetic-pole portions. In addition, since the rotor shaft functions as the inner magnetic-pole portions, it is not necessary to provide air gaps between the inner periphery of the magnet and the inner magnetic-pole portions. Therefore, the gaps between the outer magnetic-pole portions and the inner magnetic-pole portions can be set to a very small distance and the resistance of a magnetic circuit including the outer magnetic-pole portions and the inner magnetic-pole portions can be reduced. Accordingly, a large amount of magnetic flux can be generated with a small amount of current and the output can be improved. In addition, the first coil and the second coil are arranged adjacent to the magnet on substantially the same plane, and the first outer magnetic-pole portion and the second outer magnetic-pole portion are disposed so as to face the same magnet in different angular ranges. Therefore, the size of the magnet can be reduced in the axial direction and a motor with a reduced dimension in the axial direction can be provided. In addition, since the two outer magnetic-pole portions are formed integrally, error in the relative position between the two outer magnetic-pole portions can be reduced and the number of components can be also be reduced. Accordingly, a low-cost motor having a simple structure can be provided.
However, in the above-mentioned first conventional example, a mechanism for driving an optical component or the like is not particularly discussed.
On the other hand, as a second conventional example, a displacement apparatus that drives a driven member using a motor has been suggested in, for example, Japanese Utility Model Laid Open No. 2-71155.
In this apparatus, an engaging member that meshes with a screw shaft connected to the motor is attached to the driven member with a connecting member that has rigidity in a direction in which the driven member is driven and flexibility in a direction perpendicular to the moving direction of the driven member. The driven member follows the engaging member without backlash in the direction in which the driven member is driven. In addition, even when there is a parallel error between the screw shaft and guide members that retain the driven member, the error can be absorbed by bending the connecting member.
In addition, as a third conventional example, a lens-driving apparatus that drives a lens using a motor has been suggested in, for example, Japanese Patent No. 2890689.
The lens-driving apparatus includes a lens frame that holds a lens; first guiding means including two guide poles for holding the lens frame such that the lens frame can move along an optical axis; a drive shaft having a feed screw and integrated with a motor shaft; a driving piece having a notched nut that meshes with the feed screw on the drive shaft within a range of 180° or less along the circumference; and second guiding means including a single guide pole that is disposed on a motor attachment member and that holds the driving piece such that the driving piece can slide parallel to the drive shaft and rotate. The driving piece has an arm that functions as means for pinching the drive shaft. The driving piece and the lens frame are engaged with each other by insertion without a gap in the direction of the optical axis and with a gap in a direction perpendicular to the optical axis. When the drive shaft rotates, the driving piece and the lens frame are driven together along the optical axis, and the lens is moved accordingly.
In the above-described second conventional example, although the motor and the guide members must be attached to another member, explanations of such an attachment structure are not provided. In addition, the engaging member and the driven member are attached to each other with the connecting member, and a linear driving mechanism cannot be structured without the driven member. More specifically, when the driven member is newly designed, the linear driving mechanism must also be newly designed. Therefore, there is a heavy design load and it is difficult to apply this structure to devices with short product cycles.
In comparison, in the above-described third conventional structure, a linear driving mechanism can be structured without the lens and the lens frame, which correspond to the driven member in the second conventional example. The linear driving mechanism can be obtained as a unit including the motor, the drive shaft having the feed screw and integrated with the motor, the driving piece, and the second guiding means. Even when the lens and the lens frame are newly designed, the unit that functions as the linear driving mechanism can be used without any change.
In the third conventional example, the driving piece and the lens frame are engaged with each other by insertion without a gap in the direction of the optical axis and with a gap in the direction perpendicular to the optical axis. For engagement in the optical direction, a predetermined urging force that can overpower the weight of the lens and the lens frame must be provided to eliminate the backlash after insertion. In addition, the motor unit must be attached to the lens frame from a direction perpendicular to the optical axis of the lens frame. However, if the insertion position is even slightly shifted from the final attachment position in the left-right direction, a twisting force is applied to the member that generates the urging force along the optical axis after the assembly, which affects the movement of the lens frame and the transmission of load.